(Not Applicable)
(Not Applicable)
1. Technical Field
The invention relates to earth moving equipment and more particularly to an improved surface leveling device.
2. Description of the Related Art
Leveling systems such as scrapers or graders are commonly used to level relatively large areas of ground and are well known in the art. These leveling systems are commonly pushed or pulled by bulldozers, tractors, or other similar equipment.
In recent years laser beam level control systems have become more commonly used with expensive motorgrader and bulldozer leveling systems to robotically control a scraper for producing a ground contour. One such system is available from Topcon Positioning Systems, Inc. of Pleasanton, Calif. These systems provide three-dimensional machine control over the leveling and contouring of a site. A robotic tracking station is provided to communicate directly with a conventional control system on the grading machine. Using either a local positioning system or GPS technology, a computer program containing stored information concerning a desired site contour can robotically control much of the grading operation. Typically, an operator remains with the machine and manages materials, but the robotic system can be used to control the angle and depth of the grader blade. In this way, the system provides a very accurate control capability that greatly improves the efficiency and accuracy of the grading operation.
While the foregoing motorgrader systems have proved highly advantageous, they are also generally used on very large and expensive machines such as motorgraders and bulldozers. Smaller, less expensive operations often make use of smaller, relatively inexpensive box grader devices that are towed behind a conventional tractor utilizing a three-point hitch. Such systems have, in some instances, been adapted to utilize laser-leveling techniques. For example, U.S. Pat. No. 6,168,348 B1 to Meyer et al. discloses such a system. However, these types of towed scraper systems have generally not been adapted to take advantage of existing control technology for performing complex contour robotic grading.
One reason why laser contour grading has not been fully implemented in towed scraper systems is due to the difficulty of integrating a complex multi-axis movable scraper blade with a conventional tractor incorporating a simple three-point hitch system. Because conventional tractors cannot be expected to have the complex electronics and hydraulics to control the multi-axis movable scraper blade, such functions must be incorporated on the towed scraper system. Moreover, the movement of the towed scraper system and associated blade must be such as to accommodate the fixed linkage to the tractor through the conventional three-point hitch.
The invention concerns a towable scraper system for contour surface grading. The system includes a rigid chassis member that has a coupler configured for attachment to a conventional three-point tractor hitch. A scraper blade is pivotally suspended from the rigid chassis member and is equipped with a blade motivator for causing an angular rotation of the blade around an axis aligned with a towing direction. According to one aspect of the invention, the scraper blade can be configured as a box scraper.
A lift assembly raises and lowers the rigid chassis member to control a height of the scraper blade relative to a work surface to be graded. The towable scraper system is provided with a carriage assembly that offers rolling support for the rigid chassis as it moves over the work surface. The carriage assembly is pivotally coupled to the rigid chassis at a location opposed to the coupler and is configured for angular rotation around a second axis aligned with the towing direction.
According to another aspect of the invention, the blade motivator and the lift assembly are responsive to a control system for continuously varying the angular rotation and the height of the scraper blade for automatically grading a work surface to a predetermined contour. The blade motivator is comprised of a rigid support arm extending above the rigid chassis member and a hydraulic cylinder attached between an upper portion of the rigid support arm and a portion of the scraper blade.
According to another aspect of the invention, the carriage assembly can include a carriage frame with one or more wheel rotatably mounted thereto. The wheel can be designed to pivot on the pivot frame for better tracking in any selected towing direction.
The lift assembly is comprised of a lift frame pivotally connected on a proximal end to the rigid chassis member and on a distal end to the carriage assembly. The lift frame is pivotally connected to the rigid chassis member on a portion of the rigid chassis member opposed from the coupler. The lift assembly can further advantageously include a rigid support extending above the rigid chassis member and a lift motivator. The lift motivator can be a hydraulic cylinder connected between an upper portion of the rigid support and the distal end of the lift frame.